As fly heights in disc drives become smaller, accurate characterization of the inputs to air bearing simulation programs become more and more critical in achieving agreement between modeling results and fly height measurements. Suspension preload, pitch torque, and roll torque are among the inputs to air bearing simulation that need to be characterized. Accurate characterization of these forces presents a problem because they are a function of how the suspension is loaded. Currently, these forces are measured on a specially designed tester and then fly height measurements are made on a different tester. If the suspension is not loaded in exactly the same way on the two testers, then the preload, pitch torque, and roll torque will be different. The ideal situation would be to measure the loads while the head is flying on the fly height measurement tester.
A separate issue with lower fly heights is the characterization of the disc glide height and glide avalanche. The disc glide height is defined as the height at which a head starts to hit isolated asperities. The disc glide avalanche is defined as the height at which the head cannot fly any lower because it is continually in contact with the peaks on the disc. Typically the glide height and glide avalanche are measured using acoustic emission (AE) sensors. A significant problem that arises is interpretation of the AE sensor output. Many frequencies are present and it is not always clear which frequencies relate to contact and which frequencies relate simply to flying. Also, due to the very high frequencies that are usually associated with contact, the sensor, filter, and acquisition system may not be sensitive enough to detect light contact associated with an isolated asperity or the initial point of avalanche.
Embodiments of the present invention provide solutions to these and other problems, and offer other advantages over the prior art.